story #4526: Have statistics on Tracker v5

Change-Id: I151fbdedc20a6f94a757ddd2a255cc89f95e77d7
Merge remote-tracking branch 'gerrit/4526_trackerv5_statistics' into HEAD

* gerrit/4526_trackerv5_statistics:
  story #4526: Have statistics on Tracker v5

Change-Id: I7f18066fa75444d4499bfcd7881df94e970d0979
This is Tuleap 6.4.99.7

Change-Id: I6d98d54e3b6f824674b21a97f691aa37d113291e